In the lathe turning of a workpiece, the turning operation can comprise a longitudinal turning in which the tool is moved along an axis of rotation of the workpiece as well as transverse turning, e.g. facing, in which the tool is moved transverse to this axis. In copying lathes, the turning process can include a combination of longitudinal and transverse turning with portions of the process involving exclusively longitudinal turning while other portions involve exclusively transverse turning or facing.
In the turning of metal workpieces, especially with copying lathes, problems have arisen with respect to the length of the chip which is removed from the workpiece. It is not uncommon, for example, for a relatively long curled chip having a length of tens of centimeters to be produced during the turning process. Chip lengths of this magnitude are detrimental since the long curled chip, having the configuration of a helix or spiral, tends to create dangers with respect to operating personnel, can wind around parts of the workpiece and can result in shattering, vibration or the like during the cutting operation. The latter disadvantage reduces the machining accuracy and reproducibility of the parts which are to be formed on the copying lathe.
The cutting tool can comprise a so-called turning plate of a hard metal, e.g. tungsten carbide, which can be mounted on a holder, e.g. by bonding the turning plate as a tip of tungsten carbide on a conventional tool bit.
The problem with excessively long chips has confronted the art for considerable time and many effeorts have been made to develop turning tools with a controlled chip breakage, i.e. a breakage after the chip is formed and before it has exceeded a certain maximum length. These systems have been proposed primarily for longitudinal turning, i.e. the turning of long shafts, rods or bars by movement of the tool parallel to the axis of rotation of the workpiece while the same is rotated about its axis. While such systems are effective to obtain a controlled chip breakage for longitudinal turning, when the same turning plates are employed for facing, i.e. transverse turning, they produce relatively wide, thin and excessively long chips, so-called irregular chips, which are detrimental to the operations which are desired for the reasons enumerated above. The problem is especially pronounced in copying lathes or, more generally, copier turning apparatuses in which a combined longitudinal and face turning is carried out. It is necessary in such cases to remove the long irregular chips by means of chip hooks or the like and hence to constantly monitor the turning operation with operating personnel. A continuous observation of the turning process by an individual who could better be employed elsewhere is therefore necessary and fully automatic operation is not possible.